In many applications corrosion of metal articles exposed to air is a significant problem. A variety of techniques are used to reduce or prevent such corrosion. For example, metal articles have been packaged with a material containing a volatile corrosion inhibitor (“VCI”). VCIs function by slowly releasing vapors that contact the surface of the metals. The vapor phase corrosion inhibitors envelop the metal article in a non-corrosive layer and retard moisture and oxygen present in the atmosphere from attacking and reacting with the metal surfaces. Volatile corrosion inhibitors may be applied by combining the VCI with a liquid and spraying the entire surface of the metal article to be protected. Alternatively, the metal article itself may be enclosed, packaged or surrounded in or with materials containing VCIs. For example, VCIs may be incorporated into a packaging material such as paper and plastic wraps, films, and plastic dunnage. VCIs are also known to be incorporated into an emitting device with a binding matrix. Such emitters can be used within closed spaces such as packaging containers, electrical boxes, storage bags, and other enclosures. Different volatile corrosion inhibitors or combinations of volatile corrosion inhibitors may be selected based on the type of metal to be protected, the size of the enclosure, and the length of time that protection is required.
Examples of known VCI mixtures include U.S. patent application Ser. No. 11/588,885 assigned to the assignee of the present invention, which discloses a VCI mixture comprising a volatile corrosion inhibitor and a resin based binding matrix which is heated and irreversibly cured. Such a mixture is highly advantageous in that it allows for controlled release of VCIs, can be formed at relatively low temperatures and can be formed in a variety of shapes.
One of the issues with current volatile corrosion inhibitor emitting packaging materials is that the volatile corrosion inhibitor often can not be seen or detected by close inspection. This creates a number of drawbacks to the use of volatile corrosion inhibitors. For example, end users of the packaging article do not have a convenient method to confirm that the packaging article contains an appropriate volatile corrosion inhibitor mixture and an appropriate amount of the appropriate VCI mixture. Further, VCI concentrates or master batches are often sold to vendors that are contracted to manufacture packaging articles that contain volatile corrosion inhibitors. Unless expensive analytical tests are performed, it is difficult to assure that the vendor incorporated the VCI concentrate or master batch into the articles in the right amounts. In addition, many times volatile corrosion inhibiting packaging articles are sold through distribution where they are stored with numerous similar articles that do not contain volatile corrosion inhibitor. It can be difficult to differentiate between the two types of packaging articles. Also, volatile corrosion inhibitor concentrates or master batches are sometimes sold to customers that wish to produce and sell packaging articles that contain volatile corrosion inhibitors. Often times these customers buy volatile corrosion inhibiting concentrates from more than one source. If performance problems arise from the application of these packaging articles, there is no way of knowing which volatile corrosion inhibiting concentrate had the problem.
It would be highly desirable to provide a simple way of determining whether a given volatile corrosion inhibiting mixture is present in or on an article.